Structure and properties of titanium nitride thin films deposited at low temperatures using direct current magnetron sputtering

F. Elstner, A. Ehrlich, H. Giegengack, H. Kupfer, F. Richter
Technische Universität Chemnitz
Institut für Physik,
Chemnitz, Germany

Titanium nitride layers on silicon substrates have been deposited bz magnetron sputtering at a constant temperature of 200⁰C using nitrogen partial pressures (p_N2) from 0.001 to 0.36 Pa. Distinct dependenced between p_N2 in the reactive gas and the mechanical and structural properties of the layerscould be found by x-ray diffraction and other methods. The general absence of the TI₂ phase in layers deposited at low temperatures can be explained by the high energy impact of energetic particles during the deposition process as well as by the limited mobility of adatoms due to the low substrate temperature. two different cases of lattice distortions were detected for low and high p_N2, respectively. In the higher pressure range the lattice parameters a₀¹¹¹ are greater than the a₀²⁰⁰. For this the variable density of interstitial sites in different planes together with the macroscopic film stress was found to be responsible. At lower p_N2 the a₀¹¹¹ was smaller than the a₀²⁰⁰. This effect could be explained by the presence of a high number of vacancies in the lattice influencing the chemical bonding and thus leading to an anisotropy of the stability of the interplanar spacings. From that macroscopic stresses results in an anisotropic deformation of the film crystallites. Both explanations could be supported by annealing experiments.